In transmission of digital data representing a variety of signal information etc., encrypting the digital data to be transmitted at a transmission side and decrypting the encrypted digital data to reproduce the original data at a reception side are proposed in order to prevent, for example, tapping in the data transmission path. Known and typical encryption algorithms adopted in the encryption of digital data include a data encryption standard (DES) method published by the National Bureau of Standards (NBS) in the US Department of Commerce in 1977 and an advanced encryption standard (AES) method published by the National Institute of Standards and Technology (NIST) under the jurisdiction of the US Department of Commerce in 2001 (for example, refer to “ADVANCED ENCRYPTION STANDARD (AES) (FIPS PUB 197)”, Nov. 26, 2001, Department of Commerce, National Institute of Standards and Technology, Information Technology Laboratory).
Basically, in the encrypted transmission by the DES method or the AES method, digital data to be transmitted is encrypted in accordance with a rule defined in key data (encryption key data) separately provided and the encrypted digital data is decrypted in accordance with a rule defined in key data (decryption key data) separately provided. Key data (common key data) is used as the encryption key data and the decryption key data. The algorithms for the encryption and the decryption are disclosed, and the common key data is kept secret to ensure confidentiality.
In the field of video signals, digitization is encouraged in order to realize diversification of transmitted information and increase in quality of reproduced images. For example, high definition television (HDTV) systems that process digital video signals formed of digital data representing information concerning the video signals have been proposed. Digital video signals (hereinafter referred to as HD signals) in the HDTV systems are formed in accordance with, for example, the BTA S-002 standard established by the Broadcasting Technology Association (BTA) (refer to “BTA S-002 1125/60 Kouseido terebijon houshiki sutajio dhizitaru eizo kikaku”, February 1992, BTA) and have a Y-PB/PR format and a G-B-R format. In the Y-PB/PR format, Y means a luminance signal and PB/PR means a color difference signal. In the G-B-R format, G means a green primary color signal, B means a blue primary color signal, and R means a red primary color signal.
For example, each frame period in each of the HD signals is divided into a first field period and a second field period. The HD signal has a frame rate of 30 Hz (a field rate of 60 Hz), has 1,125 lines for every frame period, has 2,200 data samples for every line, and has a sampling frequency of 74.25 MHz. The HD signal in the Y-PB/PR format complies with a data format shown in FIG. 1.
In the data format in FIG. 1, reference letter A in FIG. 1 indicates part of one line in a luminance-signal data sequence (Y data sequence) representing a luminance signal component in the video signal, and reference letter B in FIG. 1 indicates part of one line in a color-difference-signal data sequence (PB/PR data sequence) representing a color difference signal component in the video signal. Each word data forming the Y data sequence and the PB/PR data sequence includes, for example, 10 bits. In other words, each of the Y data sequence and the PB/PR data sequence is 10-bit word sequence data having continuous 10-bit words and has a word transmission rate of, for example, 74.25 Mwps.
Each line of the Y data sequence has a line blanking area and video data continuously formed therein. In the Y data sequence, timing reference code data (SAV: Start of Active Video) including four words (3FF(Y), 000(Y), 000(Y), and XYZ(Y); since “3FF” and “000” are hexadecimal numbers, “h” indicating the hexadecimal number is added to “3FF” and “000”, which are represented as “3FFh” and “000h”, and (Y) indicates a word in the Y data sequence), each word including 10 bits, is arranged immediately before the video data. Timing reference code data (EAV: End of Active Video) including four words (3FF(Y), 000(Y), 000(Y), and XYZ(Y)), each word including 10 bits, is arranged immediately after the video data. Also in the PB/PR data sequence, SAV including four words (3FF(C), 000(C), 000(C), and XYZ(C); (C) indicates a word in the PB/PR data sequence), each word including 10 bits, is arranged immediately before the video data, and EAV including four words (3FF(C), 000(C), 000(C), and XYZ(C)), each word including 10 bits, is arranged immediately after the video data. The EAV and SAV in the Y data sequence are arranged in the line blanking area in the Y data sequence, and the EAV and SAV in the PB/PR data sequence are arranged in the line blanking area in the PB/PR data sequence.
Among the four words (3FF(Y), 000(Y), 000(Y), and XYZ(Y) or 3FF(C), 000(C), 000(C), and XYZ(C)), the first three words ((3FF(Y), 000(Y), and 000(Y) or 3FF(C), 000(C), and 000(C)) are provided for establishing word synchronization or line synchronization, and the last one word (XYZ(Y) or XYZ(C)) is provided for discriminating between the first field and the second field in the same frame or for discriminating between the timing reference code data EAV and the timing reference code data SAV.
In the HD signal including the Y data sequence and the PB/PR data sequence, multiple codes that includes timing identification codes forming the timing reference codes data SAV and EAV and that are not used as information codes forming the video data are defined for the Y data sequence and the PB/PR data sequence as inhibited codes. The inhibited codes are equal to 000h to 003h and 3FCh to 3FFh (hexadecimal numbers), that is, 0000000000 to 0000000011 and 1111111100 to 1111111111 when the Y data sequence and the PB/PR data sequence are 10-bit word sequence data.
Auxiliary data used for transmitting information different from the digital video signal represented by the video data is arranged in the line blanking area in the Y data sequence and the PB/PR data sequence, in addition to line number data and error detection code data. The auxiliary data is standardized in accordance with the BTA S-005B standard (refer to “BTA S-005B 1125/60 houshiki HDTV bitto chokuretsu intafeisu ni okeru hojo deta no kyoutsuu kikaku”, March 1998, ARIB) established by the Association of Radio Industries and Business (ARIB).
The standardized auxiliary data forms a data packet including a predetermined number (one or more) of words. A first format shown by reference letter A in FIG. 2 and a second format shown by reference letter B in FIG. 2 are set for the data packet formed of the auxiliary data (auxiliary data packet).
The auxiliary data packet in the first format (shown by reference numeral A in FIG. 2) includes 7 to 262 words (each word includes 10 bits). In the auxiliary data packet in the first format, a three-word auxiliary data flag (ADF), a one-word data identification word (DID), a one-word data block number word (DBN), a one-word data count word (DC), a user data word (UDW) of 0 to 255 words, and a one-word checksum word (CS) are sequentially arranged. The auxiliary data packet in the second format (shown by reference letter B in FIG. 2) differs from the auxiliary data packet in the first format in that a one-word second data identification word (SDID) is used instead of the one-word data block number word (DBN) but is similar to the auxiliary data packet in the first format in other aspects.
The ADF denotes the start of the auxiliary data packet and has continuous three words arranged therein, which are a combination of 000h, 3FFh, and 3FFh and to which the inhibited codes described above are set. The DID denotes a type of the UDW. Eight bits among the 10 bits are used for information and the higher two bits are used for avoiding the inhibited codes. The DBN denotes the order of the auxiliary data packets having the same DID. Eight bits among the 10 bits are used for information and the higher two bits are used for avoiding the inhibited codes. The DC denotes the number (0 to 255) of words in the UDW. Eight bits among the 10 bits are used for information and the higher two bits are used for avoiding the inhibited codes.
The UDW is 10-bit data which includes no inhibited code and to which a code within a range from 004h to 3FBh is set, and is information data representing information to be transmitted in the auxiliary data. The CS denotes a checksum value. Nine bits among the 10 bits are used for information and the highest one bit is used for avoiding the inhibited codes. The SDID denotes a type of the UDW, like the DID. Eight bits among the 10 bits are used for information and the higher two bits are used for avoiding the inhibited codes.
When the auxiliary data is used for transmitting digital audio information (digital audio auxiliary data), the digital audio auxiliary data is standardized, separately from the general auxiliary data, in accordance with the BTA S-006B standard (“BTA S-006B 1125/60 houshiki HDTV bitto chokuretsu intafeisu ni okeru dhizitaru onsei kikaku”, March 1998, ARIB) established by the ARIB described above.
The standardized digital audio auxiliary data also forms a data packet having a predetermined number (one or more) of words. The data packet formed of the digital audio auxiliary data (audio data packet) has the first format shown by reference letter A in FIG. 2, as shown in FIG. 3.
The audio data packet (FIG. 3) includes 31 words (each word includes 10 bits). In the audio data packet, a three-word ADF, a one-word DID, a one-word DBN, a one-word DC, a 24-word UDW, and a one-word CS are sequentially arranged.
In the audio data packet, the ADF denotes the start of the audio data packet and has continuous three words arranged therein, which are a combination of 000h, 3FFh, and 3FFh and to which the inhibited codes described above are set. The DID indicates that the content of the UDW is digital audio information. Eight bits among the 10 bits are used for information and the higher two bits are used for avoiding the inhibited codes. Specifically, for example, the DID set to a code 2E7h indicates information belonging to an audio group 1 on channels 1 to 4, the DID set to a code 1E6h indicates information belonging to an audio group 2 on channels 5 to 8, the DID set to a code 1E5h indicates information belonging to an audio group 3 on channels 9 to 12, and the DID set to a code 2E4h indicates information belonging to an audio group 4 on channels 13 to 16. The DBN, DC, and the CS are similar to those in the auxiliary data packet described above.
The UDW is digital audio information data representing digital audio information to be transmitted in the digital audio auxiliary data. In each word in the digital audio information data, the remaining eight bits, excluding the higher two bits among the 10 bits, normally serve as information bits. In each of the 24 words in the UDW, eight bits among the 10 bits are used for information and the higher two bits are used for avoiding the inhibited codes. In the 24 words, the first two words (UDW0 and UDW1) represent audio clock phase information, the 16 words from the third word to the eighteenth word (UDW2 to UDW 17) represent digital audio data, and the six words from the nineteenth word to the last word (UDW18 to UDW23) represent error correction data.
When the HD signal including the Y data sequence or the HD signal including the PB/PR data sequence, described above, is transmitted, it is desirable to realize serial transmission in which the word sequence data is converted into serial data for transmission because the data transmission path is simplified in the serial transmission. The serial transmission of the HD signals including the Y data sequence and the PB/PR data sequence is standardized so as to perform transmission in compliant with a high definition-serial digital interface (HD-SDI) in the BTA S-004 standard (refer to “BTA S-004 1125/60 houshiki HDTV shingou no bitto chokuretsu intafeisu kikaku”, April 1995, BTA) established by the BTA described above.
In the transmission compliant with the HD-SDI, word multiplexing is performed for the Y data sequence and the PB/PR data sequence in synchronization with the line blanking area having the EAV and the SAV arranged therein to form a word multiplexed data sequence shown in FIG. 4 as 10-bit word sequence data having a word transmission rate of 74.25 Mwps×2=148.5 Mwps. In the word multiplexed data sequence, multiplexed timing reference code data (multiplexed SAV) including eight words (3FF(C), 3FF(Y), 000(C), 000(Y), 000(C), 000(Y), XYZ(C), and XYZ(Y)), each word including 10 bits, is arranged immediately before the video data, and multiplexed timing reference code data (multiplexed EAV) including eight words (3FF(C), 3FF(Y), 000(C), 000(Y), 000(C), 000(Y), XYZ(C), and XYZ(Y)), each word including 10 bits, is arranged immediately after the video data.
The bits, from the least significant bit (LSB) to the most significant bit (MSB), in each of the 10-bit words in the word multiplexed data sequence are sequentially transmitted to convert the parallel data to the serial data, scrambling is performed for the serial data to generate a serial transmission HD signal (hereinafter referred to as an HD-SDI signal), and the HD-SDI signal is transmitted through the data transmission path. The HD-SDI signal has a bit transmission rate of, for example, 148.5 Mwps×10 bits=1.485 Gbps.
In the transmission of the HD-SDI signal through the data transmission path, described above, there are cases in which it is desirable that the HD-SDI signal be encrypted at the transmission side and the encrypted HD-SDI signal be decrypted to reproduce the original HD-SDI signal at the reception side in order to prevent, for example, tapping on the data transmission path to improve the security of the information transmission. In principle, the encrypted transmission of the HD-SDI signal can also be performed in the encrypted transmission system adopting the DES method or the AES method described above.
Encrypting the video data in the HD signal that forms the HD-SDI signal and that includes the Y data sequence and the PB/PR data sequence to generate encrypted video data, which include no inhibited code, forming an encrypted HD signal including the encrypted video data, performing parallel-serial (P/S) conversion for the encrypted HD signal to generate an encrypted HD-SDI signal, and transmitting the encrypted HD-SDI signal through the data transmission path have already been proposed by the applicant of this application in the patent application No. 2002-135039 filed in May 10, 2002.
Although the transmission of the HD-SDI signal including the video data subjected to the encryption through the data transmission path has already been proposed, it is desirable that auxiliary data, for example, the digital audio auxiliary data, included in the HD signal forming the HD-SDI signal be encrypted in order to further improve the security in the information transmission. Specifically, it is desirable to form an encrypted HD signal including encrypted auxiliary data, to perform the P/S conversion for the encrypted HD signal to generate an encrypted HD-SDI signal, and to transmit the encrypted HD-SDI signal through the data transmission path.
Accordingly, in the transmission of the HD-SDI signal, encrypting the UDW in the auxiliary data packet formed of the auxiliary data included in the HD signal forming the HD-SDI signal, as in the video data, to generate an encrypted UDW, forming an encrypted auxiliary data packet including the encrypted UDW, generating an encrypted HD signal including the encrypted auxiliary data packet, and transmitting an encrypted HD-SDI signal based on the encrypted HD signal are suggested.
However, the generation of the encrypted HD signal including the encrypted auxiliary data packet and the transmission of the encrypted HD-SDI signal based on the encrypted HD signal by using technologies already proposed have the following disadvantages.
First, problems can be caused at the reception side receiving the encrypted HD-SDI signal to generate the encrypted auxiliary data packet. Although such problems are not caused when the receiving apparatus receiving the encrypted HD-SDI signal to generate the encrypted auxiliary data packet from the encrypted HD-SDI signal includes decryption means for decrypting the encrypted UDW included in the encrypted auxiliary data packet to reproduce the original UDW, the problems are caused when the receiving apparatus does not include the decryption means, for example, when known receiving apparatuses are used.
For example, when the encrypted auxiliary data packet is an encrypted audio data packet including the UDW having encrypted digital audio information, a-receiving apparatus generating the encrypted audio data packet from the encrypted HD-SDI signal detects an ADF included in the encrypted audio data packet to recognize the start of the encrypted audio data packet, extracts the encrypted UDW from the encrypted audio data packet, and supplies the encrypted UDW to an audio reproducing unit. When the receiving apparatus includes the decryption means in the audio reproducing unit, the decryption means in the audio reproducing unit performs the decryption for the encrypted UDW to generate a UDW having the original digital audio information, an appropriate reproduced audio signal based on the generated UDW is generated, and the reproduced audio signal is supplied to audio reproducing means, for example, a speaker. As a result, an appropriate reproduced sound based on the appropriate reproduced audio signal is output from the speaker. In contrast, when the receiving apparatus does not include the decryption means in the audio reproducing unit, an undesired audio signal based on the encrypted UDW is generated because the decryption is not performed for the encrypted UDW in the audio reproducing unit, and the undesired audio signal is supplied to the audio reproducing means, for example, the speaker. As a result, for example, an excessive current based on the undesired audio signal is possibly applied to the speaker to damage the speaker.
Next, for example, when the encrypted auxiliary data packet is an encrypted audio data packet including the UDW having encrypted digital audio information, the encryption possibly causes a reduction in performance of the error correction of the encrypted UDW based on the UDW including an error correction code.
Furthermore, for example, a stream converter using a first-in first-out (FIFO) memory can be used for the encryption in the generation of the encrypted auxiliary data packet. In such a case, since some lines in the Y data sequence and the PB/PR data sequence forming the HD signal are largely occupied by the auxiliary data, the writing period for the FIFO memory is not sufficiently provided to cause a state in which the FIFO memory is emptied. As a result, a reduction in quality of the encryption security of the encrypted auxiliary data packet is probably caused.
In the generation of the encrypted HD signal including the encrypted auxiliary data packet and the transmission of the encrypted HD-SDI signal based on the encrypted HD signal, having the above disadvantages, it is desirable that the encryption be selectively performed for every auxiliary data packet in each line in the Y data sequence and the PB/PR data sequence forming the HD signal in order to improve the flexibility in the actual use.
The present invention described in the claims of this application provides a data transmission method capable of generating the encrypted auxiliary data packet by the encryption of the auxiliary data packet formed of the auxiliary data included in a signal, such as the HD signal, forming the HD-SDI signal, capable of generating the encrypted signal, such as the encrypted HD signal, including the encrypted auxiliary data packet, and capable of transmitting the serial signal, such as the encrypted HD-SDI signal, based on the encrypted signal such that the disadvantages involved in the application of the above known technologies that have been proposed can be avoided and the encryption can be selectively performed for every auxiliary data packet, and provides a data transmission apparatus implementing the data transmission method. In addition, the present invention provides a data reception method capable of receiving the serial signal, such as the encrypted HD-SDI signal, formed and transmitted based on the encrypted signal, such as the encrypted HD signal, including the encrypted auxiliary data packet, the encrypted auxiliary data packet being generated by the encryption of the auxiliary data packet formed of the auxiliary data included in a signal, such as the HD signal, forming the HD-SDI signal, capable of generating the encrypted signal, such as the encrypted HD signal, and the encrypted auxiliary data packet from the serial signal, such as the encrypted HD-SDI signal, and capable of performing the decryption for the generated encrypted auxiliary data packet to reproduce the auxiliary data forming the original auxiliary data packet, and provides a data reception apparatus implementing the data reception method.